Telephone-exchange system



Aug. 10 1926. 1,595,084

C- L. GQODRUM El AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25,1924 9 Sheets-Sheet 1 Aug. 10 1926.

c. GOODRUM ET AL TELEPHONE EXCHANGE SYSTEM Filed Nov. 25,.

Aug. 10 1926. 1,595,084

C. L. GOODR UM ET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25,1924 9 sheets sheet 5 Aug. 10 1926.

C. L. GOODRUM ET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25.1924 9 gh Aug. 10,1926. 1,595,084

C. L. GOQDRUM ET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25,1924 9 Sheet //7l/6/770/5Z' 6/20/1931. fiaadmmdfar/JHbsm Aug. 10, 1926.1,595,084

. C. L- GOODRUM ET AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25,1924 9 Sheets-Shet 6 Mar/:91. 6004/11/27 dfar/ J. 6115500 I Aug. 101926. 1,595,084

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TELEPHQNE EXCHANGE SYSTEM Original Filed Nov. 25, 1924 9 sheets-sheet sAug. 10,1926. 1,595,084

7 C. L. GOODRUM El AL TELEPHONE EXCHANGE SYSTEM Original Filed Nov. 25,1 9 Sheets-Sheet 9 lnrenfarx- Mar/e: L. 6004mm die/l J. 67 80 FatentedAug. 10, i926.

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PAT]:

I TELEJ?HOI TE-EXCZ-LANGE SYSTEMV Application filed November 25, 1924,Serial No. 752,093. Renewed October 7, 1925.

This invention relates to telephone exchange systems in general and moreparticularly to telephone systems of the automatic type whereinselectively operable switches are employed in the coi'itrolling' andcompletion of conversational connections.

The invention is particularly applicable to telephone systems such ass'hpwn and do scribedin the patent to S. B. Williams, No. 1,517,331,issued Dec. 2 192 i, in general to telephone systems wherein coordinateswitches are employed for the extension of calling lines. In thesesystems it has been the practice heretofore to terminate subscriberslines, ascalling lines, in vertical rows of contacts of thecoordinate'line switches, there being a plurality 0t subscribers lines appearing ina single switch. Each subscrib ers line apoearing in one of theseswitches has access to a number of horia 'ntal link circuits which inturn are accessible to a plurality of trunks leading to successiveselective stages. It has also been the practice heretofore to multiple asubscribers line before a number of horizontal links in a particularsection of the line switch, and also to multiple each of the outgoingtrunks before all the links of this same section. thus a calling linewould have access to an idle trunk by means of any one of a plurality oflink circuits in any given section of the switch. However, should allthe links in this section be busy when the subscriber initiates a callthe selection or an outgoing trunk would be temporarily preventedvregardless of the number of idle trunks available.

This invention has for its object, therefore, to provide improved systemfor extending calling subscribers lines by means of switchesautomatically responsive to the removal of a receiver at a callingstation.

The foregoing object is obtained by haveach subscribers lineappearbefore all the links in a particular section of t coordi nate lineswitch and by having each outgoing trunk appear before but one ink inthis section.

Ateature of the invention relates to the means for controlling theselection of a trunk which is common to a number of line switches.

A. further feature of the invention resides in the means for testingavailable paths Fig, 8 shows the temporarily non-available when such alink or trunk 18 unavailable to acalling line.

Other teaturesand advantages of the in vcntion not specificallymentioned will be revealed after a consideration of the followingdescriptions and the appended claims.

Referring to the drawing, Fig. 1 shows a plurality of subscribers lineswhich terminate in contacts of the line switches such as shown in Figs.2, 5 and 8. In the lower por tion of Fig. l is shown a portion of themaster controlling equipment normally associable with the subscriberslines shown in Fig. l.

Fig. 2 discloses a portion of a line switch of the coordinate typetogether with the re maining portion of the master switch shown in Fig.1.

Fig. 8 in the upper portion shows the cross-point test relays which areassociable with the links in the different sections of switch 200 andwith the group of trunks 270. This'figure also shows a number ofsocalled directional control relays.

Fig. 4 shows corresponding equipment to that of 1. In this instance,however, the equipment is associated with a different line switch.

Fig. 5 shows a second line switch of the coordinate type wherein adifferent group of calling subscribers lines terminate.

Fig. 6 shows the cross-point relays, which are associable with the linksof switch 500 and with the trunks in group 280. I

Fig. 7 shows a third group of subscribers lines terminating in thecontacts of athird lineswitch. V H

line switch in which the third groupof subscribers lines terminate. I

- Fig. 9 discloses the crossspoint test relays associable'with the linksof switch 800 and with the group of trunks 290-. I PT Fig. 1 0 disclosesthe manner in hichthe various figures of the drawing are to be ar-Reynolds, No. 1,515,785, issued November 18, 1924. T his type of switchconsists mainly of a number of vertical rows of contacts each row beingcontrolled by a corresponding Vertically disposed operating member.Arranged for cooperation with the vertical rows of contacts, are anumber of horizontal link circuits, each link circuit having anoperating member individual thereto. Calling subscribers lines areterminated in contacts of certain of the vertical rows, these rowscommonly being known as line Verticals. Outgoing trunks are terminatedin contacts of other vertical rows which are known as trunk verticals.Consequently, the operation of a line vertical magnet, a trunk ver ticalmagnet and a particular horizontal member determine the selectiveoperation of the switch in extending a calling line. For a more detaileddescription of the mechanical construction and operation of this kind ofswitch, reference may be had to the above mentioned U. S. Patent to S.B. Williams.

In the drawing are shown a number of these switches namely, switches200, 500 and 800. An inspection of the drawing will reveal the fact thateach trunk is multipled before a corresponding link in each of theswitches; and furthermore, that each trunk is multipled before one linkin each section of the switches. For example, trunk 221 which is thefirst trunk in group 2T0, has an appearance before the first link insection 214 of switch 200. This same trunk has an appearance before acorresponding link in a corresponding section of switch 500. The sameholds true of the appearance of this trunk in switch 800. Furthermoretrunk 221 has an appearance before the first link in section 234: ofswitch 200, and before a corresponding link in each of the switches 500and 800. A similar arrangement holds true of the remaining trunks. Itwill be observed that each subscribers line is multipled to have anappearance before all the links in any one section, for example, line110 has an appearance before all the links of section 21 1- in switch200. Similarly, line 410 has an appearance before the group of linksincluding link 501 in switch 500. It will be noted, therefore, that eachsubscribers line is accessible to all the links of the section beforewhich it is multipled and to all the outgoing trunks in each of thegroups 270, 280 and 290. For example, line 110 is accessible to trunks225, 220, 229, 230, etc., by means of link 217. Line 110 is alsoaccessible to trunks 223, 224, etc., by means of link A similararrangement obtains with trunk groups constitutes a first, second andthird choice for extending a calling line through switch 200. When asubscriber whose line terminates in switch 200, for example thesubscriber at station 101, removes the receiver, line relay 103operates, in turn causing the operation of start relay 202. Relay 202 isindividual to the row of contacts as 219, wherein the calling lineterminates. Relay 202 operates relay 204:, which looks in series withmaster relay 109 and prevents a second calling line from being extendeduntil the extension of the line 110 is completed through switch 200.Relays 109, 110, 112 and 113 form part of a master controlling circuitwhich is normally inclividual to switch 200. This master circuit timesand controls the operation of switch 200 to select a trunk in group2'70. The master circuit having been seized by the operation of relay109, line vertical magnet 205 is operated as well as the directionalrelay 303. Relay 303 associates the group of links 21 1 and the trunksin group 2'70 with the test relays 300. Each of the test relays isdouble wound, the upper winding being con nected to the sleeve conductorof a corre sponding trunk, while the lower winding is associable bymeans of directional relay 303 with the group of links before which thecalling line appears. The particular group of horizontal links to beassociated with relays 300 is determined by means of the operation ofone of the relays 105, 165, etc. 'lhe test relays are designed tooperate when either one or both of their windings are energized, thatis, when the upper winding is connected to a busy trunk or the lowerwinding is connected to a busy link.

Should all the trunks in group 270 or all he links in the selected groupbe busy when the call is initiated, the selection of a trunk in thesecond choice group, namely, group 280 is begu However, trunks 280constitute the iii t choice for switch 500. Accordingly, with all thecross pointrelays 300 operated, a circuit is completed for relay 114;,causing the master circuit of switch 500 to be associated with switch200. This is accomplished by operating a transfer relay 412, which inturn operates directional relay 601 and releases directional relay 803.Relay 601 associates the test relays 600 with the links in section 21-5and with the trunks in group 280. Should there e fist an idle crosspoint, then the proper trunk vertical jun switch, a second choice "formagnet and horizontal magnet in switch 20 are actuated under jointcontrol of the nuts ter circuits of witch 200 and switcl 50. whichrelease when the id e trunk is SEZGQ. Should all the cross point relays600 be operated when directional relay 601 is actated, indicating thateither all linlzs in so; tion 214 or all trunks in group 280 be a thirdtransfer relay is operated. lay 713 causes the master circuit of switcn700 (which controls the group of trun 290 as first choice) to beassociated w switch 200. Relay 601 is thereupon releas and relay 901operated'instead. l .i associates the linlrs of section an: the trunksin group 290 with test relays 900. Should there exist an idle crosspoint, the the corresponding relay remains 110i and switch 200 isactuated to seize the trunk in group 290. In this case the seis': of theidle trunk is under joint control it the master circuits of switches Wand 700.

Should the calling subscribefis line he l oated in switch 500, then theselection 0: trunk is made in group 280 first choice, or in group 290.as second choice, group 270 as third choice. Similarly, shoind thecalling line be located in switch 800, the se lection of an idle trunkis begun in group 390 as first choice, group 270 as second choice andgrou 280 as third choice. For example, should all trunks in the firstchoic of switch 800, nainely, group 200 be busy, transfer relay 181 isoperated the mas ter circuits of switches 200 and 800 operate to seize atrunk in group 2?0. Should all trunlrs in group 270 be busy, transferrely 482 is operated and the seizure a in group 280 is placed undercontrol of the master circuits of switches 5-00 and 800. Thus, it willbe seen that any given group of trunks constitutes a first choice toronean other switch another switch.

ud a third choice for still lVhilc the invention has been shown appliedto three line switches and three groups of trunks, it is understood thata greater number of switches and the same number of groups of trunks maybe employed. .Also for the sake of preserving simplicity in the drawingthere has been shown a comparatively number of trunks in a group andeach group has been shown occupying but two vertical rows of contacts.In practice, however, afar greater-number of trunks occupying acorrespondingly greater number of vertical rows may be employed. it willbe noted that the relays of groups 300, 600 and 000, etc.,'are eachindividual to a trunk even though this trunk is inultipled before anumber of switches. @onsequently, the number of cross point test relaysis siderably less than the possible number of available cross pointsthrough the several line switches. This is accomplished by at hereinafteand the selection 01 a t ll it-h relay 20 i operated pelowing the testrela s to be associated'by nieans 01" the directional relays 301, 302,803, 601, 602, 603, etc., with the links of any switch. I

Detailed description.

ion the subscriberat station 101 re s the the purpose of initiating acall, line operates by means of a circuit 'nclurles the closed loop or"the call- .;.nd the'left grounded contacts of ut-on relay Assuming thatthere an idle inlr, such as 21'4", in secs itch 200, then relay 10'? isnorexist tion rial, and the-operation or" the line relay completes acircuit from vground throug tie left contacts or" relays 107, 103andl-Su,

to battery through the winding of start re- 202. Assuming that themaster control circuit shown in the lower portion of Figs.

and 2 is idle at the time the call is initi- As soon, therefore, asrelay Alas attracted its arinatures, a circuit is completed from ground,through the left ter c ntact of relay 11.1,right cont-acts of relay 113,thence through the normal contacts of elay 109, contacts of relay 1S2,conduct-or right inner contacts of re 202 to battery through the leftwinding of relay 5204i. Relay 2041 upon attracting its arinatures closesa locking path which may be traced through the right winding and innerright contacts tor 1Z5, winding of relay 109, to gror the normalcontacts of relay 110. Belay operates in this circuit. With relay 100actuated an energizing circuit i coinplet d for directional relay Thiscircuit may be traced from battery, through the winding of relay B03,conductor rightinner armature and back contact or relay 114:,lett ariiature and Iront contac of relay 109 to the grounded conductor Belay 303out *ds'this re ground through its left armature and front contact toconductor winding; oi relay 119 to battery.

Relay 119 is slow to operate and req lll'CS an appreci contacts. it willbe observed that the cir- 'cuit above traced for operating directionalrelay 503 includes nornial contacts of relay 11 Should there have beenno avilable paths to the group of trunl-r 270 appearing in rows and 211,then relay 114: wi-nild 1. o 'g. i be operated in tneinannei to be u d21 SLlCQ ecing group would be il ll tor the present it may be ass; ethat there exi ts such an idle path. relay 114 is non; al and the abovetra-e operating circuit is coin leted for relay 80'.

completed through-the vino receiver from the switchhooh,

or". said relay, conductical magnet 205, and through the right windingof relay 203, thence through the left middle contacts of relay 204,conductor 162, right armature and front contact of relay 109, to thegrounded conductor 159. Should a subscriber whose line is in a differentvertical group from that including line 101, have initiated a callsubsequent to the actuation of line relay 103, then the vertical startrelay individual to the second group and similar to relay 202 isoperated, thus providing a locking circuit for relay 203. In addition,relay 203 in operating brings about the release of start relay 202, thuspreventing a second calling line in the first vertical group beingextended before the calling line in the succeeding vertical group hasbeen extended.

Horizontal group relays 105 and 106 now operate in a circuit traceablefrom battery, through their operating windin s in par allel, thencethrough contacts of relays 107 and 108, right contacts of relay 103, conductor 157, left outer contacts of relay 201, left normal contacts ofrelay 112 to the grounded conductor 159. Relay 105 locks through itsright winding and locking contacts, thence through the winding of masterswitch relay 112 to ground as above traced. Relay 112 operates in thiscircuit. A locking circuit is now completed for relay 106, which may betraced from battery through the left winding and locking contacts ofsaid relay, left outer contacts of relay 105, right contacts of relay110, left armature and front contact of relay 112 to the groundedconductor 159. Itwill be noted that the above traced circuit is alsoextended in parallel through the winding of relay 108, which operates.lVith relay 112 operated a circuit is completed from battery through thewinding of relay 30d, conductor 152, right contacts of relay 110, leftarmature and front contact of relay 112, to grounded conductor 159.

It will be assumed that all the trunks having an appearance in verticalrow 210 are busy, either as a result of their being connected to callinglines through contacts of switch 200, or through switch 500, or throughswitch 800. For example, trunk 221 may be connected to line 410 by meansof a link, as 501 in switch 500, thus rendering trunk 221 nonselectableat switch 200. Similarly, the remaining trunks which ap ,pear invertical row 210 of switch 200 and in corresponding vertical rows 510and 810 of other line switches are assumed to be nonselectable. It willbe further assumed that trunk 226 which appears in vertical rows 211,511 and 811 of the several line switches is the first idle trunk in thefirst group of trunks 2?0. It will also be assumed that horizontal link215 is busy, while horizontal links 216 and 217 are idle.

An inspection of Figs. 2 and 3 will render clear the relation of thevarious cross point test relays to the corresponding trunks. Forexample, relay 321 is individual to trunk 221 and is in an operatedcondition when this trunk is non-selectable. Relay 323 is individual totrunk 223, relay 325 to trunk 225 and similarly for the remainingrelays. While but two sections of switch 200 are shown and but sixtrunks terminating therein, it will be understood that there may be agreater number of sections and a greater number of trunks, dependent ontraffic conditions. Since trunks 221, 223, 225, etc., in vertical row210 are busy, then the corresponding cross point relays 321, 323, 325,etc., are operated. Accordingly, the operating circuit for trunkvertical magnet 231 is broken at the upper inner armatures and backcontacts of these relays. Since, however, trunk 226 is assumed to beidle, relay 326 individual thereto is normal, and a circuit may betreated from battery, through the winding of trunk vertical magnet 218,conductor 251, contacts of relay 303, conductor 357, upper innerarmature and back contact of relay 326, upper inner armatures and frontcontacts of relays 324, 322, 325,

etc.,in series, conductor 353, left inner contacts of relay 204,conductor 156, contacts of relay 119, to ground through the rightarmature and front contact of relay 109. lVith magnets 205 and 218operated, the release of the master switch is initiated, under thecontrol of the timing relays 110 and 113, which are designed to be slowin operating. The period elapsing between the initial energization ofrelay and the complete operation of relay 113 is suflicient to ,permit atest to be made of the horizontal links in section 214: of switch 200and to permit the operation of a horizontal magnet corresponding to anidle link in this section. Accordingly, relay 110 is energized by meansof circuit which may be traced from battery through its winding,conductor 158, lower inner armatures and front contacts of magnets 205and 218 to ground. After an interval when'relay 110 has completelyattracted its armatures, it closes an obvious energizing circuit forrelay 113, which also attracts its armatures after an interval haselapsed. I 7

Since the calling line is accessible to a plurality of links in section214, including links 215, 216, 217, etc., and since the idle trunk 226has an appearance before link 217 alone in this section and furthermore,since link 216 has been assumed idle, While link 215 has been assumedbusy, it becomes necessary to render link 216 momentarilynon-selectable. This is accomplished by the operation of the start wireadvance relay 116, which is individual to link 216. Since link 215 hasbeen assumedbusy, relay 115 is ene 'ized through both it igs of magnetlett wlndn of relav 116, contacts of relay 106,

conductor 161, contacts of relay 303, lowermost armature-s and frontcontacts of relays 32-1: 3 conductor 361, right outer contacts of l .v114.. to the wounded conductor 150. Should there be other idleintervening lllllKS'bQiWcQll link 2 6 and link 217 the relays similar torelay 116 are energized in circuits corresponding to that already tracedtor'relay 116. It to be noted that the resistance or" the left windingsor relays 115, 116, etc, is sulliciently high to prevent the operationor" the corresoonding horizontal magnets 225, 226,etc. ltelays 115 and 16 lock through their right windings and locking contacts thencethroughthe left inner contacts of relays 105 and 108, right contacts of relay103, conductor 157, left outer contacts of relay 201;, lower outerarmatures and front'contacts of magnets 205 and 218 to ground. Sinetrunk2 6 is idle, relay 117 ren ains normal when magnet is energized,whereupon a circuit is completed fronrba-ttery through the right windingof magnet 237, right armature and back contracts of relay 117, rightarmatures and front contacts ot preceding. relays 116-, 115. etc., toground, as above traced. Magnet 22? completesalocking' circuit traceablefrom hattery hrough both windings in series with the left winning ofrelay 117, thence through contacts-in row 210, test conductor of link21?, contacts in row 211, sleeve conductor of trunk upper outer armatureand'back contact of relay 326, lower outer contacts of 30%, upper innerarmature and front 5 of relays 324, 322, 325, etc., in seri sto'groundover conductor 353, as hereinoetore traced. Relay 117 does not operateat this time, however, since it is shunted by the original energizingcircuit traced for magnetili 'l. The calling line 110 is now cry to edmeans. of link 21'? to the idle trunk w ereupon the sleeve conductor ofthis trunk is maintained grounded at a suc.- roding selective switch, asdescribed in deail in the above me tioned patent to S. B. 'Villiams.

At the end of the interval determined by heoperation of relay'113, whenthis relay s completely attracted its armature, the iolding circuit forrelay 201 and master relav 109 broken, these relays thereupon release.The holding circuit of horizontal oup relay 105 and master relay 112 isalso lnoken at this time. The release of relay 20% opens the energizingcircuits of relay 203 and. the line vertical magnet 205. Magnet-205..thereupon restores to normal. Relay 10am relea iopens theenergizing circuit of the directional control relay 303, which in turncauses the release of trunk vertical magnet 218. lVith relay 105 normalthe shunt is removed from around the winding '11? and this relayenergizes in seall 'nhetore traced. Since link 216 was aseration, thelocking circuit through the right vinding of this relay is broken by therelease of the master switch, thus releasing relay 116 and restoringlink 216 to its seloct'ble condition. 1t will be noted, however, thatlink 215 which was assumed busy when the. master switch was seized, isstill ed to he idle at the initiation of the 010- the windings of magnet237, as

maintained busy by the continued energizetion of the horizontal magnet235 in series with the left Winding of relay 115 to the grounded sleevetest conductor of the busy link 215. ll ith the in ster switch restoredto normal, relay 30% releases, whereupon the shuntis removed from aroundthe upper wining of relay .d this relay now 0 crates in a circuit whichmay be traced from battery, tirough the upper winding thereof, to thegrounded sleeve conductor of trunk As soon as through switch 200,cut-oil relay 104 operates and releases the line relay 103. Theconnection is now in a stable condition and the master switen associatedwith frame 200 is rendered available in controlling other connections.

AZZ pat/ts busy in, first group. I

It will next he assumed that both trunks 2 and 226, which are the lasttrunks appearing in rows 210 and 211, respectively, are alone idle, whenthe master switch is seized, b 217 givi ac ess to these 311": whilepreceding linlzs, as 216, The sequence of operations onditions issimilar to that alueseriher, as far as the point where iest niadc. Inthis case, not selectable, line 110 cannot he ezi to either of thetrunks and 226, even though these trunks are idle at the time.Accordingly, with relays 303 and 106 operated, s hereinhefore described,a circuit is coi'n leted from battery, through the lower windings ofrelays and 326 in parallel. contacts of: relay 303, conductor ht innercontac sleeve conductor of link 217. Since link 2 17 is the only link insection 21-1 that gives the calling line access to the idle trunks 225and 226 and since both these trunks have been thus renderednon-selectable by the operation of relays 325 and 326, line 110 cannotbe extended to any trunk in the first group with wnich the master switchshown in Fig. 1 is associable. It will be seen, therefore, that all thecross-point test cs 0t relay 106, thence the connection is'establishedrelays associated with the first group of trunks are operated either asa result of the corresponding trunks being busy or as a result of theavailable links being busy- Tl'iereforc, it is necessary to perform atest of the trunks in group However, since the selection of a trunk ingroup 280 is controlled by the master circuit of switch 500. this mastercirc -.it must be associated temporarily with switch 200. Accordinglywith all the cro s-point test relays of the first groin) oper' d, abovedescribed, a circuit is completed from battery through the right windingof relay 114i, conductor 656, lower inner arn'iatures and front contactsof relays 326, 324, etc., in series, to ground. Relay 11 1 is as; ciatedwith switch 200 and is individual to the first group of trunks 270 whichincludes trunks 221', 222, 223, etc. A locking circuit is completed forrelay 11% which may be traced from battery through the left winding andlocking contact thereof, thence to the grounded conductor 159.Assun'iing that there exists an idle trunk in group 280, then relay 41%which is individual thereto is normal, and it becomes necessary toassociate the master switch shown in Fig. 4t with switch 200. Theassociation of this second master switch is initiated by the operationof transfer relay 4:12. This relay operates in a circuit traceable frombattery through its winding, left contacts f relay 126, left armatureand back contacts of relay 41 i, conductor 435 right inner armature andfront cont ct of relay 114:, left armature and front contact of relay109, to grounded conductor 159,. Assuming the master switch shown inFig. l to be idle when relay 4:12 operates, a circuit is now closedthrough the right winding of relay 4125, left outer armature and frontcontact of relay 4112, right outer armatures and back contacts of relays502, 508, etc, in series, contacts of relay 433, right armature and backcontact of relay 109, left normal contacts of relay 410, conductor 452,to ground at the armature of relay 111. Relay 125 operates and thereuponcloses a locking circuit: through its left winding and locking contact,winding of relay 438, to ground tl'irough the left contacts of relays410 and 111. Relay 4:33 operates in this circuit and renders the masterswitch associated with switch 4-00 busy. he preceding circuits werecompleted under the assumption that no subscriber. whose linetern'iinates in switch 400, had initiated a call at the instant that themaster switch was seized by the operation of relay 412. Should such asubscriber have initiated acall immediately prior to the operation ofthe relay 182, a corresponding start relay 502, or 503, would beoperater'l, thus preventing relay 125 from operating: and seizing thismaster switch. The calling subscriber, whose line terminates in switch200, must, therefore, await the release of the master switch which isindividual to switch 1:00.

i /hen relay 1-25 operates an energizing circuit is closed for relay 126which may be traced from battery through the left winding thereof, rightouter contacts of relay 4-25,

left outer armature and back contact of relay d1 1, conductor 451,rightinner armature and front contact of relay 11st, to ground throughthe left armature and front contact of relay 109. Relay 496 looksthrough its right winding and locking contact provided another relasimilar to relay 412 is ener gizcd. Bela also closed an operatingcircuit for d1:ectional relay 601. This circuit may ll-' traced frombattery through the winding thereof, conductor 652, right outer contactsof relay 125, left armature and back contact of relay e14, to thegroundcd conductor 4:51. Relay 601 extends this same ground throughitsleft contacts to conductor 656, thence to battery through the windingof slow operating relay 419.,

The relation of the cross-point relays 627, 628, 629, etc, to the groupof trunks 280 is similar to that already described in connection i 'ithrelays 321, 322, etc., and the trunks in group 270. The drawing showstrunk 227 as l'iaving an appearance before the first link in section214, while trunk 229 is shown as appearing before the last link in thissame section, it being understood that other trunks will. haveranappearance in row 212, each before a different link in section 2141. Asimilar arrangement holds truefor the trunks appearing in vertical row213. It will be assumed that link 217 is the only idle link in section21d, and that trunks 227, 228 and 230 are the only idle trunks in group280. Since, however, link 215 which gives access to the idle trunks 227and 228 is busy, it becomes necessary to render these trunks momentarilynon-selectable while a test is being made of the available cross pointsin switch 200. 7

Since link 215 is busy, a circuit may be traced from battery through thelower windings of relays 627 and 628 in parallel, contacts of relay 601,conductor 651, conductor 152, right outermost contacts of relay 106, tothe grounded test conductor of link 215. The operation of relays 627 and628 renders trunks 227 and 228 momentarily non-selectaale. Since it hasbeen assumed that all remaining links in section 21 1 are idle, it isnecessary to render all these links tempo-- rarily non-selectable withthe exception, however, of link 217 before which the idle trunk .30appears. Accordingly, relay 116 is operated by means of a circuitcompleted from battery through the windings of magnet 236, left windingof relay 116, rightconta ts of relay 106, conductor 161, contacts ofrelay 601, lowermost armature and front contacts of relays 632 and 631,conductor 653, right outer contacts of relay 414 to ground through theleft contacts of relay 410. Similar circuits may be traced forsucceeding relays corresponding to 116 and associated with remainingidle links ,in' section 214. The corresponding circuit for operatingrelay 117, however, -is broken at the lowermost contacts of relay 630,which relay is normal at this time. l/V hen relay .419 has closed itscontacts a circuit for trunk bring about the release of the masterswitch associated with the frame 200. At this time also a paralleloperating circuit is com- )leted through the winding of the releaserelay 410. This circuit may be traced from battery through thewinding ofrelay 410, right inner contact of relay 425, conductor 455, thence tothe grounded conductor 158. Relay 410 after an interval causes relay 413to operate, whereupon ground is removed from the windings of relays 425and 433 and these relays release. Relay 425 causes release ofdirectional relay 601. The master switch of Fig. 4 is thus released forcontrolling other connections. The connection through the switch 200 ismaintained by magnet 237 which is locked in series with the left windingof relay 117, contacts or" switch 200 to the grounded sleeve conductorof trunk 230. It will be noted that release of directional relay 601opens the previously traced operating circuits for the relays 116, etc,associated with the idle links in switch 200. lVhenthe group relay106'releases the locking circuit of these relays is broken and the samerelease to render .the associated links selectable.

All pat/ 2s busy-in first and second groups.

tions it will be noted that because of thebusy condition of link 215,trunk 228 can not be selected regardless of its being idle.

The onerations in this case are similar to those already'described inconnection with. the selection of a trunk 1n group 280, relay contact of.r

412 operating as already described to asso ciate the master circuit oiswitch 500 with lWltCh 200. in this case, however, when the ss-pointtest is to be made and since trunk alone is assumed to be idle, then allof cross-point relays shown in Figs. 3 and re operated with theexception of relay 28 which is individual to the cross-point deerminedby trunk 228 and link 215. i-rcco dingly, when directional relay 601oper- GDCD I ates as above described, a circuit is closed irom batterythrough the lower winding of relay 028, contacts of relay 601,conductors 651 and 152, right outer contacts 01 relay 106 to thegrounded test conductor of link 215. All the cross-point relays havingthus been operated as an indication that no available paths exist togroup 280, relay 414 is oper' ated by means of a circuit which maytraced from battery through the right wind- J th reof, conductor 655,lower inner ar- .res and front contacts of relay 630, 032, etc, inseries to ground. Relay 414 immediately locks through its left windingand locking contact, to ground through the left arinatures of relays 410and 111. Relay 414 at its left armature and back contact opens thepreviously described enei lug circuit o1 relay 601 which thereuponreleases in turn causing the release of relay 628. All the reiainincross-point relays shown in Figs.

3 and 6 being maintained energized b means of the grounded sleeveconductors of the associated busy trunks.

The master switch shown in Fig. 7 which is individual to switch 800 isnext associated with the third group of trunks 290. Assun. ing that anidle trunk exists in this group. relay 714 is normal, and transfer relay713 operates, by means of a circuit completed from battery through thewinding thereof, left contacts of relay 72*", middle armature and backcontact of relay 714, cond .ctor 751', left outer armature and front cotact of relay 414, conductor nence to ground through the right innerarmature and front 4 elay i4.

shown in Fig". 7 to be idle t en this'latter relay locks by means oi scuit completed through its left winding and in l ng contact in serieswith the winding of relay 715. Belay 715 perates in this circuit andrenders the associated master switch busy. Di-

rcctional relay 901 is now operated in a cir cuit traceable from battery.hrough the winding of said relay, conductor 952, right outer contactsof relay 725, left middle armature and back contact of relay 714, toground over conductor 751 above traced. 901 in turn causes energizationof slow operating relay 719. l Vith relay 901 operated the cross-pointtest relays 900 are associated.

with the group of trunks 290 and with the links in section 214-. In amanner similar to that already described in connection with thecross-point relays of groups 300 and 600, an idle path is determined insection 214 which gives access to a trunk in group 290 and the properhorizontal magnet corresponding to this idle path is actuated. As soonas a trunk vertical magnet, for example magnet 233, is operated groundis extended as hereinbefore described over conductor 158, to operaterelay 110, and over conductor 455 to operate relay 410. This same groundis extended by means of conductor 755 and the right inner contacts ofrelay 425 to the winding of release relay 710. In a manner deemed to bealready familiar, rela s 1.10, 410 and 710 bring about the release ofthe associated master switches and also the release of magnets 20'") andIn the foregoing detailen description. it has been assumed that thecalling subscribe ers line terminates in contacts of sw .ch 200 withwhich the master switch shown in the lower portions of Figs. 1 and 2 isrmrinaly associated. Should, however, tln. calling no be located in adifferent line srmh, for example, switch 500 the s of an idle trunk ingroup 280 will take plac. since the master circuit of switch 500 isnormally sociable with this group of trunks. Should all available pathsin this group be busy when the subscriber at station 401 initiates acall, then relay 414 operates. The circuit for operating relay 414 maybe traced from battery, through the right winding thereof, conductor655, thence through the lower inner contacts of all the busy cross-pointrelays 600 to ground. Relay 414 locks and brings about the release ofdirectional relay 602, which it will be noted is operated in a circuitsimilar to that hereinbefore described in connection with relay 301.Assuming there to he an idle trunk in group 290, then relay 714 isnormal, and a circuit is closed for transfer relay 723. This circuit maybe traced from battery, through the winding of relay 723, left contactsof relay 724, left outer armature and back contact of relay 714.conductor 752, r' 'ht inner armature and front cont-act of relay 414,left armature and front contact of relay 4-09 to ground through the leftcontacts of relays 410 and 111. In a manner deemed to be alreadyfamiliar, the operation of transfer relay 723 brings about the actuationof directional relay 902 and the subs quent association of the masterswitch'of Figs. 7 and 8 with switch 500 whereby an idle trunk in group290 is selected. Should, however, all paths to trunks in groups 280 and290 be simultaneously busy, then relays 414 and 714 are operated. Relay714 locks and causes the release of directional relay 902. A circuit isalso completed for transfer relay 121 which may be traced from battery,through the winding thereof, left contacts of relay 123, left middlearmature and back contact of relay 114, conductor 756,

left outer armature and front contact of relay 714, conductor 752, rightinner armature and front contact of relay 414 to ground. Relay 121causes the successive actuation of relays 122, 123 and directional relay302. Relay 302 associates the cross-point relays 300 with the horizontallinks of switch 500 for the purpose of selecting an idle path in switch500 as hereinbefore described.

Similarly, should the calling line terminate in switch, 800 then uponthe removal of the receiver by the calling subscriber start relay 803operates in turn causing the operation of relay 804 which looks inseries with relay 709. A line vertical magnet as 805 and directionalrelay 903 thereupon operate and the cross-point relays 900 areassociated with the links in switch 800 and with the group of trunks290. Sho-uld there be an idle trunk in this group, and an available linkgiving access thereto, then the corresponding horizontal magnet isoperated to complete the extension of the calling line. The release ofthe master switch as brought about by the actuation of relay 710subsequent to the operation of a trunk vertical magnet as is alreadydescribed. -The release of the master switch in turn causes the re--circuit of directional relay 903 which re leases. Should one of therelays 300 be released indicating an idle trunk in group 270, then relay114 is normal and transfer relay 131 operates. the actuation ofdirectional relay 301 and the association of cross-point relays 300 withthe links of switch 800 and the trunks in group 270. Should all therelays 300 be operated, indicating an all-trunks busy condition in group270, then relay 114- operates in turn releasing relay 301. l-Vith relays1.14 and 714 operated, a circuit is closed for transfer relay 432 whichassociates the mas-' ter switch. of Figs. 4 and 5 with the switch 800.Subsequently, a trunk and horizontal magnet of switch 800 are operatedshould there be an available path to an idle trunk in group 280, andthis idle trunkis seized. as already described in detail.

hat is claimed is:

1. In combination, subscribers lines arranged in groups, an automaticswitch for extending said lines comprising groups of link circuitscorresponding to said groups of Relay 131 brings about.

lines, outgoing trunks each accessible to but one link in each of saidgroups of links, testing devices for said trunks and each associablewith a link in any of said groups of link circuits, and means dependentupon the condition of said testing devices for causing said switch tooperate to seize a trunk.

In combination, subscribers lines arranged in groups, an automaticswitch responsive to the initiation of a call on any of said lines forextending the same, groups of link circuits in said automatic switchcorresponding to said groups of lines, a plu rality of outgoing trunks,each trunk accessible to but one link in each ofjsaid groups of links,testing devices for said trunks and each associable with a link inany ofsaid groups of link circuits, and means for actuating said switch toseize one of said'trunks de endent upon the condition of the assosiatedtesting devices. 7

3. In combination, subscribers lines arranged in groups, an automaticswitch responsive to the initiation of a call on any of said linesforextending the same, groups of link circuits in said automatic switchcorresponding to said groups of lines, a plurality of outgoing trunkseach trunk accessible to but one link in each of said groups of links,testing relays for said trunks and each associable with a link in any:of said groups of link circuits, and means for actuating said switch toseize one of said trunks dependent upon the condition of the associatedtestingrelay. y

4:. In combination, subscribers lines arranged in groups, an automaticswitch for ergtending said lines and comprising groups of link circuitscorresponding to said groups of lines, outgoing trunks, eachtrunkaccessible to one link in each of said groups of links, a pluralityof testing devices, each associable with a trunk and associable with alink in any of said groups, means dependent upon the condition of saiddevices for operating said switch to connect a link to a line and to anidle outgoing trunk.

5. In combination, subscribers lines arranged in groups, an automaticswitch for extending said lines comprising groups of link circuitscorresponding to said groups of lines, outgoing trunks, each trunkforming a cross point with one link in each of said groups of links,testing devices each individual to a trunk and associable with thecorresponding link in each of said groups of links, means dependent uponthe condition of said devices for operating said switch toconnect a lineand to a trunk, and means responsive to said connection for renderingall cross points involving said link non-selectable.

6. In combination, subscribers lines arranged in groups, an automaticswitch for extending said lines comprising groups of link circuitscorresponding to said groups of lines, outgoing trunks each trunk havingan appearance before one link in each group of links, each appearanceforming a cross point for completing connections, testing devices eachindividual to a trunk and as sociable with a plurality of said crosspoints, and means dependent upon the condition of said testing devicesfor causing said switch to operate to extend a calling line through anidle one of said cross points.

7. In combination, subscribers lines arranged in groups, automaticswitches for ex-- tending said lines, said switches comprising groups oflink circuits corresponding to said groups of lines, a plurality oftrunks com: mon to all of said switches, each trunk having an appearancebefore one link in each group of links in all of said switches, testingdevices accessible in common to all of said switches and each individualto one of said trunks, means responsive to the busy condition of a trunkfor operating the device individual thereto to render said trunknon-selectable at all'of said switches. and means dependent upon thecondition of said devices for operating one of said switches to seize anidle one of said trunks.

8. In combination, subscribers lines arranged in groups, automaticswitches for extending said lines each switch comprising groups of linkcircuits corresponding to said groups of lines, a plurality of trunkscommon to all of said switches, each trunk having an appearance beforeone link in each group of links of all of said switches, a plurality oftesting device-s each individual to a trunk and associable with a linkin any of said switches, and means dependent upon the condition of thetrunks and the links with which said devices are associated foroperating one of said switches to seize an idle one of said trunks.

9. In combination, subscribers lines arranged in groups, automaticswitches for extending said lines, each switch comprising groups of linkcircuits corresponding to said groups of lines, a plurality of trunkscommon to all of said switches, each trunk having an appearance beforeone link in each group of links of all of said switches,

a plurality of testing devices each individual to a trunk and associablewith a link in any of said switches, and means responsive to theinitiation of a call and dependent upon the condition of the trunks andthe links with which said devices are associated for operating one ofsaid switches to seize an idle one of said trunks.

10. In combination, subscribers lines ar ranged in groups, automaticswitches for extending said lines, each switch comprising groups of linkcircuits corresponding to said groups of lines, a plurality of groups oftrunks each trunk having an appearance in all of said switches, testingdevices each individual to a trunk, means for associating certain ofsaid devices with a particular group or" links in any one of saidswitches, and means dependent upon the condition of said group of linksand the corresponding group of trunks for associating in successionother of said test devices with said group of links, for the purpose ofextending a line to a trunk in another group of trunks.

11. In combination, subscribers lines arranged in groups, automaticswitches for extending said lines each switch comprising groups oi linkcircuits corresponding to said groups of lines, groups of trunks eachtrunk appearing in all of said switches, said groups constituting aplurality of successive choices for extending one ot said lines, testingdevices arranged in groups corresponding to said groups of trunks, each"device individual to a trunk, means for associating a first group ofdevices with any group of link circuits, means dependent upon thecondition oi said group of link circuits for successively associatingother groups of devices with said group of link circuits, and meansdependentupon the condition of any group of devices for operating one ofsaid switches to extend a line by means of a link in said group of linksto an idle one of said trunks.

12. In combination, subscribers lines arranged in groups,automaticswitch-es for extending said lines comprising groups of link circuitscorresponding to said groups of lines, groups oi trunks constitutingsuccessive groups oi choices i or extending said lines, testing deviceseach individual to a trunk, means for associating a portion of saiddevices with a particular group of links in one of said switches, meansdependent upon the busy condition of said links in said group and thecondition of the first choice trunks for associating other portions ofsaid devices in succession with said group of links to seize a trunk ina succeeding choice group.

13. In combination, subscribers lines ar ranged in groups, automaticswitches for extending said lines comprising groups of link circuitscorresponding to said groups of lines, a plurality of trunks, eachtrunkada ted to form a junction with one link in each group of links, testingdevices less in number than the number ofsaid junctions, means forassociating said devices in succession with diilerent groups ofjunctions forthe purposeoi making a test thereof, and means dependentupon the finding of an idle junction for operating said switch to seizesaid junction to extend a calling line there through.

let. In combination, subscrihe rs.,lil es arranged in groups, anautomatic'switch in which said lines terminate andxconiprising groupso-filin'k circuits, groups of trunks appearing in contacts of saidswitch, said trunks and links forming groups of junctions for extendingcalling lines, testing de vices arranged in groups corresponding to saidgroups of trunks each device individual to a trunk, means iorassociatinga group of devices with a first group of junctions, means dependent upona busy condition of said first group of junctions for associating insuccession other groups of testing devices with remaining groups ofjunctions, and means effective upon the finding of an idle junction inany group for operating said switch to extend a calling linetherethrough.

In witness whereof, we hereunto subscribe our names this 24th day ofNov-ember A; D.,

ARLES 'L. GOODRUM. EAR-L S. GIBSON.

